package main

import (
	"bytes"
	"context"
	"encoding/json"
	"net"
	"net/http"
	"os"
	"os/exec"
	"os/signal"
	"path/filepath"
	"strings"
	"syscall"
	"testing"
	"time"
)

// The tests run main() in a child process, this test binary started
// again with runMainEnv set, because main() can exit its process and
// takes its settings from the environment.
const runMainEnv = "NETWATCH_SERVER_RUN_MAIN"

// childTimeout bounds each child's whole run; it is killed after it.
const childTimeout = 10 * time.Second

func TestMain(m *testing.M) {
	if os.Getenv(runMainEnv) != "" {
		// A SIGTERM that comes before fx catches it is dropped, not fatal.
		signal.Notify(make(chan os.Signal, 1), syscall.SIGTERM)
		main()

		return
	}

	os.Exit(m.Run())
}

// TestOutputIsJSONWithoutFxLines: off a terminal, every line the server
// writes from start to stop is JSON, and without DEBUG none of them is
// one of fx's.
func TestOutputIsJSONWithoutFxLines(t *testing.T) {
	t.Parallel()

	stdout, stderr := runServerUntilStopped(t)

	requireJSONLines(t, stdout, stderr)

	if !strings.Contains(stdout.String(), `"msg":"starting"`) {
		t.Fatalf("no startup line in stdout:\n%s", stdout)
	}

	if strings.Contains(stdout.String(), `"msg":"started"`) {
		t.Fatalf("fx line in stdout without DEBUG:\n%s", stdout)
	}
}

// TestDebugLogsFxLines: with DEBUG set, fx's lines are logged, as
// JSON, from the start to the signal that stops the server.
func TestDebugLogsFxLines(t *testing.T) {
	t.Parallel()

	stdout, stderr := runServerUntilStopped(t, "DEBUG=1")

	requireJSONLines(t, stdout, stderr)

	for _, msg := range []string{"started", "received signal"} {
		if !strings.Contains(stdout.String(), `"msg":"`+msg+`"`) {
			t.Fatalf("no fx line %q in stdout with DEBUG set:\n%s",
				msg, stdout)
		}
	}
}

// TestRefusedSettingIsLastLine: a setting the server refuses stops the
// start, and the one error line logged is the last, naming the setting
// and why, without fx's text around it.
func TestRefusedSettingIsLastLine(t *testing.T) {
	t.Parallel()

	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
	defer cancel()

	child, stdout, stderr := startServer(ctx, t, t.TempDir(),
		freePort(ctx, t), "REPORTS_PER_MINUTE=0")

	err := child.Wait()
	if child.ProcessState.ExitCode() != 1 {
		t.Fatalf("server exit = %v, want exit status 1", err)
	}

	if stderr.Len() != 0 {
		t.Fatalf("stderr = %q, want nothing", stderr)
	}

	lines := strings.Split(strings.TrimSpace(stdout.String()), "\n")

	for _, line := range lines[:len(lines)-1] {
		if strings.Contains(line, `"level":"ERROR"`) {
			t.Fatalf("an error line before the last line:\n%s", stdout)
		}
	}

	var last struct {
		Level string `json:"level"`
		Error string `json:"error"`
	}

	err = json.Unmarshal([]byte(lines[len(lines)-1]), &last)
	if err != nil {
		t.Fatalf("last line is not JSON: %v\n%s", err, stdout)
	}

	want := `REPORTS_PER_MINUTE "0": must be a positive whole number`
	if last.Level != "ERROR" || last.Error != want {
		t.Fatalf("last line has level %q, error %q; want ERROR, %q\n%s",
			last.Level, last.Error, want, stdout)
	}
}

// runServerUntilStopped runs main() in a child process with env added
// to its environment, waits until it answers its health check, stops it
// with SIGTERM and returns its stdout and stderr. It fails the test if
// the child does not exit cleanly.
func runServerUntilStopped(
	t *testing.T,
	env ...string,
) (*bytes.Buffer, *bytes.Buffer) {
	t.Helper()

	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
	defer cancel()

	port := freePort(ctx, t)
	child, stdout, stderr := startServer(ctx, t, t.TempDir(), port, env...)

	waitForHealthcheck(ctx, t, port)

	// The child drops a SIGTERM that comes before fx catches it (see
	// TestMain), so send one every 100ms until the test ends. ctx
	// bounds the wait: when it ends, the child is killed.
	stop := make(chan struct{})
	defer close(stop)

	go func() {
		for {
			_ = child.Process.Signal(syscall.SIGTERM)

			select {
			case <-stop:
				return
			case <-time.After(100 * time.Millisecond):
			}
		}
	}()

	err := child.Wait()
	if err != nil {
		t.Fatalf("server exit = %v, want success", err)
	}

	return stdout, stderr
}

// TestMalformedConfigFileStopsTheStart: a config file the server finds
// but cannot read stops the start, and the error is logged as JSON.
func TestMalformedConfigFileStopsTheStart(t *testing.T) {
	t.Parallel()

	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
	defer cancel()

	home := t.TempDir()
	dir := filepath.Join(home, ".config", "netwatch-server")

	err := os.MkdirAll(dir, 0o750)
	if err != nil {
		t.Fatal(err)
	}

	err = os.WriteFile(filepath.Join(dir, "netwatch-server.yaml"),
		[]byte("PORT: [8080\n"), 0o600)
	if err != nil {
		t.Fatal(err)
	}

	child, stdout, stderr := startServer(ctx, t, home, freePort(ctx, t))

	err = child.Wait()
	if child.ProcessState.ExitCode() != 1 {
		t.Fatalf("server exit = %v, want exit status 1", err)
	}

	requireJSONLines(t, stdout, stderr)

	if !strings.Contains(stdout.String(), "netwatch-server.yaml") {
		t.Fatalf("no error naming the config file in stdout:\n%s", stdout)
	}
}

// TestRefusedSentryDSNStopsTheStart: a SENTRY_DSN that Sentry refuses
// stops the start, and the error, naming SENTRY_DSN, is logged as JSON.
func TestRefusedSentryDSNStopsTheStart(t *testing.T) {
	t.Setenv("SENTRY_DSN", "not-a-dsn")

	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
	defer cancel()

	child, stdout, stderr := startServer(ctx, t, t.TempDir(), freePort(ctx, t))

	err := child.Wait()
	if child.ProcessState.ExitCode() != 1 {
		t.Fatalf("server exit = %v, want exit status 1", err)
	}

	requireJSONLines(t, stdout, stderr)

	if !strings.Contains(stdout.String(), "SENTRY_DSN") {
		t.Fatalf("no error naming SENTRY_DSN in stdout:\n%s", stdout)
	}
}

// TestPortInUseExitsWithStatus1: a server whose port is already taken
// cannot listen, and stops with exit status 1.
func TestPortInUseExitsWithStatus1(t *testing.T) {
	t.Parallel()

	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
	defer cancel()

	var lc net.ListenConfig

	taken, err := lc.Listen(ctx, "tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}

	defer func() { _ = taken.Close() }()

	_, port, err := net.SplitHostPort(taken.Addr().String())
	if err != nil {
		t.Fatal(err)
	}

	child, stdout, _ := startServer(ctx, t, t.TempDir(), port)

	err = child.Wait()
	if child.ProcessState.ExitCode() != 1 {
		t.Fatalf("server exit = %v, want exit status 1\n%s", err, stdout)
	}
}

// startServer runs main() in a child process listening on
// 127.0.0.1:port, with home as its HOME and working directory and its
// data directory in home, so it touches nothing outside home. env is
// added to its environment, as NAME=value strings. Its
// stdout and stderr go to the two buffers returned, which hold all of
// it once child.Wait returns. The child is killed when ctx ends, and
// killed and reaped when the test ends if nothing waited for it.
func startServer(
	ctx context.Context,
	t *testing.T,
	home, port string,
	env ...string,
) (*exec.Cmd, *bytes.Buffer, *bytes.Buffer) {
	t.Helper()

	self, err := os.Executable()
	if err != nil {
		t.Fatal(err)
	}

	var stdout, stderr bytes.Buffer

	child := exec.CommandContext(ctx, self) //nolint:gosec // this test binary
	child.Dir = home
	child.Env = append(os.Environ(),
		runMainEnv+"=1",
		"HOME="+home,
		"DATA_DIR="+filepath.Join(home, "data"),
		"BIND_ADDRESS=127.0.0.1",
		"PORT="+port,
	)
	child.Env = append(child.Env, env...)
	child.Stdout = &stdout
	child.Stderr = &stderr

	err = child.Start()
	if err != nil {
		t.Fatal(err)
	}

	t.Cleanup(func() {
		if child.ProcessState == nil {
			_ = child.Process.Kill()
			_ = child.Wait()
		}
	})

	return child, &stdout, &stderr
}

// freePort returns a TCP port on 127.0.0.1 that was free a moment ago.
func freePort(ctx context.Context, t *testing.T) string {
	t.Helper()

	var lc net.ListenConfig

	l, err := lc.Listen(ctx, "tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}

	_ = l.Close()

	_, port, err := net.SplitHostPort(l.Addr().String())
	if err != nil {
		t.Fatal(err)
	}

	return port
}

// waitForHealthcheck returns once the health check on port answers 200.
func waitForHealthcheck(ctx context.Context, t *testing.T, port string) {
	t.Helper()

	url := "http://127.0.0.1:" + port + "/.well-known/healthcheck"

	for {
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
		if err != nil {
			t.Fatal(err)
		}

		resp, err := http.DefaultClient.Do(req)
		if err == nil {
			_ = resp.Body.Close()

			if resp.StatusCode == http.StatusOK {
				return
			}
		}

		select {
		case <-ctx.Done():
			t.Fatalf("health check never answered: %v", err)
		case <-time.After(50 * time.Millisecond):
		}
	}
}

// requireJSONLines fails the test on each line of outs that is not
// JSON.
func requireJSONLines(t *testing.T, outs ...*bytes.Buffer) {
	t.Helper()

	for _, out := range outs {
		for line := range strings.Lines(out.String()) {
			if !json.Valid([]byte(line)) {
				t.Errorf("line is not JSON: %s", line)
			}
		}
	}
}